The Petroleum System From Source to Trap

The Petroleum System From Source to Trap by Leslie B. Magoon and Wallace G. Dow | PDF Free Download.

Foreword to The Petroleum System From Source to Trap PDF

For years, petroleum geologists, whether working for themselves, small or large companies, or research, academic, or governmental institutions, have struggled to come up with a more reliable and logical way to judge and describe the petroleum potential and attendant exploration risks of undrilled prospects, plays, and basins.

The volume you are holding, The Petroleum System-From Source to Trap, finally solves this problem. In a collection of individually authored papers, including case studies and analogs, it describes the petroleum system approach.

While not a panacea, this exciting, if not totally new, the approach can significantly help geologists evaluate and communicate the petroleum potential and exploration risks involved in an area of investigation.

Perhaps equally important, it can provide both the data and a logical basis for constructive discussion among petroleum geologists knowledgeable in that particular area.

As a petroleum geologist with over 40 years of experience, I have seen this approach successfully employed.

It is my hope that more and more petroleum geologists around the world will not only embrace and use the petroleum system approach but will build upon and improve it.

Preface to The Petroleum System From Source to Trap eBook

The petroleum system concept was first developed in 1970 at the Amoco research laboratory in Tulsa, Oklahoma.

In my first major geochemical study, I described three "oil systems" in the Williston basin based on analytical data generated by Jack Williams and the geochemical research group, headed by Jim Momper.

The purpose was to reduce risk by predicting the most likely places where oil would be found and where it most likely would be absent.

After graduating from Rutgers University in 1959 with a B.A. in geology, three years in the military, and receiving an M.S. in geology from the University of North Dakota under Wilson Laird, I took a job with the Pan American Petroleum Corporation (now Amoco) in their Denver Division office.

I was an exploration geologist, alternating between project and well-site work in the northern Rocky Mountain area.

Jim Momper, a senior geologist I knew in Denver, had been transferred to the Tulsa geochemical research group and asked me to collect crude oils whenever possible because they needed samples to analyze. 1 collected over 250 oil samples between 1966 and 1969, about half of which were from the Williston Basin.

Because of my interest in geochemistry, Jim offered me a transfer to the Tulsa Research Laboratory to help him bring geologic insight into the then-new science of petroleum geochemistry.

I accepted the challenge and arrived in Tulsa with my family on a snowy New Year's Eve in 1969 with little idea of what the future would bring.

I have been involved in geochemistry ever since. Jack Williams analyzed the oils I had collected using techniques that were far less sophisticated than those in use today.

The Williston basin oils were clearly divided into three major genetic types with several subtypes and mixtures.

The oil compositional differences indicated that three separate source rocks were involved. Cores from all available organic-rich rocks in the basin were solvent extracted, and the extracts were analyzed with the same techniques used on the oils.

Ordovician rock extracts positively correlated with the oil found in Ordovician and Silurian reservoirs rocks, Bakken shale extracts were very similar to the oils in Mississippian and Devonian reservoirs, and extracts from Tyler shales compared favorably to oils produced from Pennsylvanian Tyler reservoirs.

Extracts from other organic-rich rocks lacked similarity to any of the oils I had collected. These analytical results and our interpretation demonstrated that oils from different source rocks can be different and that oil-source rock correlations are geologically meaningful.

In the early 1970s, it was generally known but largely ignored, that traps, reservoirs, seals, and source rocks were all required to make an oil accumulation.

Most geologists knew a lot about traps and reservoirs, little about seals, and virtually nothing about source rocks.

A few source rock papers had appeared in the 1960s by workers now accepted as pioneers in the field-Hunt, Philippi, Tissot, and Vassoyevich-which served as a foundation for our work. We did the best we could in an era before biomarkers, vitrinite reflectance, Rock-Eva! pyrolysis, capillary gas chromatography, and most of the analytical techniques we take for granted today.

Despite these difficulties, Jack's oil-source rock correlations have survived the test of time. My job was to find ways to make this new geochemical information useful to Amoco's exploration effort in the Williston basin and eventually to all petroleum provinces around the world.

I reasoned that if we knew where the oils came from and how they migrated, we could better predict where they would be found in the future. Geochemistry could then be used to high-grade areas in which to concentrate on exploration activity, thereby reducing risk.

The first step was to map the stratigraphic and areal distribution of each oil type. We were fortunate to start with the Williston basin because the three oil types are distinct here and the accumulations of each type are isolated by evaporite seals.

I identified three source-reservoir packages that I called "oil systems" and named them after their principal source and reservoir rocks. Each oil system had an area of mature source rock, migration pathways, reservoirs, traps, and seals.

The concept depended on the ability to separate oils into genetic types, correlate each type of specific source rock, estimate the quantity of oil generated and expelled from the source rock, and map the vertical and lateral migration pathways through which the oil moved.

This study led us to conclude that the combination of geology and geochemistry would become a powerful exploration tool.

We did not know it at the time, but our work had predicted most of the successful Williston Basin oil plays of the 1970s and 1980s and that little or no oil would be found in areas that we considered high risk.

After presenting our work within Amoco, we were granted permission to share our concept with the petroleum industry. Jim Momper and I organized a session on "New Ideas: Origin, Migration, and Entrapment of Oil" for the 1972 AAPG Annual Convention in Denver, Colorado.

Jack Williams presented a paper on "Characterization of oil types in the Williston basin" and I followed with a paper on 'The Application of oil correlation and source rock data to exploration in the Williston Basin." These papers were later published in the July 1974 AAPG Bulletin.

Our approach of combining geochemical data into a complete geological framework formed the basis for the petroleum system concept.

Subsequent work by Perrodon, Meissner, and Ulmishek developed these ideas further and set the stage for Les Magoon's rigorous definition and application of the petroleum system concept, beginning in 1986.

Don Mathews, vice-president of the Superior Oil Company, heard my Williston basin paper in Denver and offered me the opportunity to start a geochemical group at their research center in Houston.

Superior had just acquired a new kerogen maturity technique called "vitrinite reflectance" that was being used at the time only by Shell and Tenneco.

One of our biggest geochemical limitations in those days was the lack of a reliable way to measure the thermal maturity of organic matter independent of kerogen type. I immediately recognized the potential of this new and largely undeveloped technique, and after considerable soul searching, I reluctantly left Amoco in the fall of 1972 to begin a new adventure.

The petroleum system concept blends petroleum geology and geochemistry together in a way that can substantially increase exploration success. It is a tool that has evolved during the past 25 years and will continue to be improved in the future.

This book makes our current state of knowledge available to every company involved in the search for oil and gas, and we hope many will benefit from the ideas it contains.

For the editors, this book has a two-fold purpose-to describe the petroleum system and to provide a mechanism for evaluating migration from the active source rock to the trap. Wally and I developed the petroleum system for different reasons.

After graduation, I went to work for Shell Oil Company in Los Angeles as an exploration geologist with an emphasis on petroleum geochemistry.

Although I lacked previous experience, because I had more chemistry than most geologists I became immersed in source rock geochemistry to carry out my assignment, which was to participate in the evaluation of the offshore lease sale area in the Santa Barbara Channel.

When I entered Shell, the company was taking the geochemical research work of Phillippi from the laboratory to the field.

Since little published literature was available, I relied mostly on company documents and a small cadre of Shell geologists and geochemists who understood source rock geochemistry, such as John T. Smith, Adrian Maaskant, Marian Downey, Archie Hood, and John Castano, all of whom willingly shared their knowledge with me.

The source rock study of the Ventura basic Santa Barbara Channel area was completed in 1968, and I was transferred to Farmington, New Mexico, then on to Denver in 1971 where I carried out similar source rock studies to support new plays in both the southern and northern Rocky Mountain states.

In addition to getting well site experience, I also had the opportunity to develop a play and evaluate prospects that could be drilled.

With company training classes, my experience with exploration tools and techniques, such as paleontology, wireline logs, and geophysical data, grew quickly.

In 1972 while in Denver, I attended the AAPG session on "New Ideas: Origin, Migration, and Entrapment of Oil." Wally Dow presented one of two papers on source rock geochemistry of the Williston Basin.

Afterward, my colleagues at Shell, and I commented on how similar our approaches and interpretations were for understanding the distribution of hydrocarbons in the Williston Basin.

At the time, I was working a little farther west in the Big Snowy trough so I could relate to their interpretation in the Williston Basin.

In late 1973, I was transferred to Shell Pectin and moved to Houston. In 1974, I took a job with the USGS in Menlo Park, California, and had the opportunity to work on the Cook Inlet area in Alaska. My first assignment was to evaluate the Federal OCS of Lower Cook Inlet in preparation for an offshore lease sale.

In 1977, I was assigned to work on the North Slope in the newly named National Petroleum Reserve in Alaska (NPRA) on an evaluation effort of the previously named Naval Petroleum Reserve no.

4 (NPR-4). With George Claypool, we carried out an in-depth source rock and migration study. Around 1981, my involvement in the Arctic National Wildlife Refuge (ANWR) began.

During this time, I was involved in both national resource assessments and the third was being organized. I had the privilege of participating in Leg 77 of the Deep Sea Drilling Project (DSDP) in the Caribbean in December 1982.

Here, I was able to reflect and read a great deal about petroleum geochemistry.

Because I was involved in the national resource assessments of undiscovered oil and gas and because I realized how difficult it is to incorporate geologic information into the assessment process, I felt it would be worthwhile to develop a scheme that would better serve our purposes.

Because our organization was without reflection seismic data that could map potential hydrocarbon traps, we needed a method to evaluate the entire country systematically without seismic data. In addition, our geologic staff was much smaller and less focused than in the industry.

Obviously, a different approach than the industry used was needed to get science into the assessment process.

I began by reflecting on the way evaluations were carried out while I was with Shell and the way petroleum geology and geochemistry were being presented in the literature.

Through many discussions with colleagues, it became apparent that basin studies were a catch-all phrase for any type of work relating to sedimentary rocks and petroleum and that source rock and migration studies were poorly defined.

In addition, mass balance calculations seemed to be the best approach to determine the upper limit of petroleum available to trap, but it was unclear which factors should be included in the mass balance equation.

With the problem outlined, I presented the solution in several ways In 1986, I circulated internally a brochure about the petroleum system and how it could be used to set up the mass balance equation.

That same year, I presented a poster session at the Gordon Conference on Organic Geochemistry where Wally Dow reminded me that he had already defined such an "oil system" in 1972 in Denver and that he had published it in the AAPG Bulletin in 1974.

From 1987 to 1991, I developed the petroleum system concept and presented these ideas as a poster session during the 1987 AAPG Annual meeting in Los Angeles, at the 28th International Geological Congress in Washington, D.C., during 1989, and in the 1990-1991 AAPG Distinguished Lecture tour.

Wally Dow and I teamed up to co-convene the successful oral session (by the same name as this volume) for the 1991 AAPG Annual meeting in Dallas. Over this same time period, I have edited three U.S. Geological Survey Bulletins on the petroleum system.

During 1992 and 1993, Wally and I have visited many oil companies to acquaint their staffs with the petroleum system concept.

The help and support of many people, those mentioned above and others, are acknowledged. Ken Bird and George Claypool have always been open and direct in their suggestions and criticisms during the development of the concept.

I thank Gary Hill and Don Gautier for approving the USGS petroleum system project so that I could develop the concept.

The authors and co-authors of every chapter ensured the success of this book by allowing the editors sufficient latitude to incorporate the petroleum system concept.

Zenon Valin is gratefully acknowledged for his help in proofreading each chapter and with other duties as well. The editors appreciate the reviewers, Gerard Demaison, Miner Long, John T. Smith, and Peter van de Kamp, who read and made valuable suggestions that improved the volume.

We thank all those geoscientists who spoke up and criticized the petroleum system concept and made it more useful.

Lastly, the petroleum system concept will evolve as more case studies are published, which will undoubtedly require that the concept be continually improved.

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